1. Field of the Invention
The present invention relates generally to apparatuses for use in polymerase chain reaction (hereinafter referred to as “PCR”) and more particularly, to an apparatus for performing insulated isothermal PCR.
2. Description of the Related Art
In the filed of biotechnology, polymerase chain reaction (PCR) is a well-known technology used to amplify specific nucleic acid sequences. The PCR process comprises three major steps including denaturation, primer annealing and extension, which require different reaction temperatures. The required temperature for the denaturation step is typically in a range between 90° C. and 97° C. The required temperature for the primer annealing step will depend on the melting temperature of the primer used. Typically, the annealing temperature ranges from 35° C. to 65° C. The required temperature for the extension step is typically about 72° C.
The convective PCR is generally performed by immersing the bottom of a test tube which contains a reaction mixture into a hot water in such a way that the rest portion of the test tube is exposed to atmosphere at room temperature for heat dissipation. As a result, the temperature of the reaction mixture will gradually decrease from the bottom of the reaction mixture having a temperature of about 97° C. toward the liquid level of the reaction mixture having a temperature of about 35° C. Because of the temperature gradient, the heat convection is induced, such that the reaction mixture will flow through various regions having different temperatures and then undergo different reaction steps.
In the conventional convective PCR apparatus, high-temperature vapor generated above the surface of the hot water will convectively flow upwardly and then affect the heat dissipation around the middle and upper sections of the test tube, resulting in that the temperature at the level of the reaction mixture may not be lowered enough to the required temperature for conducting the primer annealing step. In addition, fluorescence is commonly used to detect the completion of PCR reaction. That is, a fluorescent dye is added into the reaction mixture and a laser ray is used to stream through the bottom of the test tube to the reaction mixture to detect the intensity of the fluorescence light. In the conventional apparatus for convective PCR, since the bottom of the test tube is immersed in the hot water for being heated, the hot water will badly affect the laser ray, making fluorescent detection impossible.